Electric signal switch for pneumatic tires



Aprll 30, 1946. I I E. w. CRANMER 2,399,168

ELECTRIC SIGNAL SWITCH FOR PNEUMATIC TIRES Filed Dec. 8, 1944 E I IIIIIIIIII YIIIIIIII IIIIIIIIII III,

25 waw* Patented Apr. 30, 1946 ELECTRIC SIGNAL SWITCH FOR PNEUMATIC TIRES Ernie W. Cranmer, Wichita, Kans.

Application December 8, 1944, Serial No. 567,132

2 Claims.

This invention relates to an electric signal switch for pneumatic tires, and has for its principal object a means to obviate closing the circuit by centrifugal force.

A further object of the invention is to provide a. switch extending through the rim of a wheel to receive a direct radially disposed force from a tube within a casing carried by the wheel to break an electric circuit.

A still further object of this invention is to provide a spring actuator to close the circuit when the tube has lost its force of expansion by virtue of leakage.

A still further object of this invention is to provide in the switch structure a plunger as one side of the circuit, said plunger being moved radially by the pressure in the tube toward the center of the wheel breaking the circuit. To avoid premature closing of the circuit that otherwise would occur during high velocity of rotation, the weight of the plunger is reduced by forming the same into a hollow tubular shell having a head concavo-convex, in which case the shell of the plunger and its head may be of light gauge high textured steel or of a preferred alloy of aluminum.

A still further object of this invention is to construct a pneumatic tire actuated switch having a simple and eiflcient means to secure the switch structure to the rim of the wheel.

These and other objects will hereinafter be more fully explained, reference being had to the accompanying drawing forming a part of this specification, and in which like characters will apply to like parts in the different views.

Referring to the drawing:

Fig. l is a cross section through the rim and brake drum of a wheel.

Fig. 2 is an enlarged longitudinal section through the switch mechanism.

Fig. 3 is a view taken on line 3-3 in Fig. 2 looking in the direction of the arrow.

Fig. 4 is a cross section taken on line 4-4 in Fig. 2.

Fig. 5 is a longitudinal section taken on line 55 in Fi 1.

As a more concise description of the invention as disclosed in the drawing, it will be seen that the switch is secured to and extends through the rim l of a motor vehicle wheel. The components of the switch comprise a tubular plunger 2 having a head A on one end thereof, said head hav ing an annular groove B on its outer side to receive a terminal convolution of a coil spring 3 seated therein to secure the spring axially with the tubular plunger, while the other end thereof has a portion threaded inward of its length to engage in the bore of a hub 4 that is positioned in the concavity of a concavo-convex head 5 said head 5 being positioned on the center zone of said wheel rim. The said plunger is carried slidably in the head of an insulating member 6, said insulating member being axially bored inward from its end opposite its head to function as a housing for the coil spring and also to receive a removable metallic head 1 threadedly engaging in the bore at its outer end. The last said head has an annular flange 0 surrounding its outer end to engage one end of a metallic sleeve 8 that slidably engages on the said insulating member whereby the switch structure is secured removably to the wheel rim by clamping the same between the other end of the sleeve and flange D of the first said head of the insulating member as the last said metallic head I is screwed inward at the open end of the insulating member.

To adjust the spring to a desired tension and retain the same axially in the bore of the in-' sulating member, it will be seen that the inner end of the metallic head is bored axially a spaced distance inward to receive the other terminal end of the spring movable inward and outward and being carried by a head E of a threaded stem 9 that axially engages in and through the last said metallic head to tension the spring, the stem having a slot in its outer end to be engaged by a screw driver while the head on the other end is shouldered and having a reduced extension to enter the coils of the spring and turn therein as the stem is turned.

Seated in the bottom of the bore of the insulating member is a washer-like element In that flts snugly therein and through which the plunger extends slidably but not in contact therewith as its head A is positioned to contact the washer like element which in turn transmits the electric current through the medium of a wire conductor II having one end secured to washer l0 and to a suitable signal that is visible to a. driver of the vehicle and the said wire conductor being connected to a battery carried by the vehicle as its source of electric power.

It will be understood that the said coil spring is the actuating means to move the head of the tubular plunger toward and in contact with the washer in the absence of pressure within the tube when the same is in a state of deflation, in which instance the electric current is closed. When the tube is properly inflated its pressure upon the concavo-convex head is of sufficient force to counteract power of the coil spring and its coaction with centrifugal force created by high velocity of the wheels rotation, in which instance the current is broken.

To insure operativeness, I wish to further explain that the tubular plunger slidably engages within a metallic sleeve [2 secured rigidly in the insulation to provide a smooth sliding fit for the tubular plunger to make and break the electric circuit promptly. To maintain electric current continuously to the switch mechanism during rotation of the Wheels, it will be seen in Fig. 1 that a brush contact I3 is positioned in the brake drum I 4 by a bracket l5 carried by a wire binding post IE to a plate I! that is rigidly secured to an axle housing and to which a brake shoe is secured against rotation with the wheel, said brush adapted to engage on an annular metallic member it? that seats in an annular insulation element I9 secured to and rotatable with the brake drum. To supply current to the metallic annular memher, it will be seen that one of the wheel bolts 26 is bored axially to receive an insulated conduit 2| secured in the bore and through which a conductor 22 extends and being connected to the annular metallic member by a wire 23, the other end of said wire being secured to the wheel bolt conductor by a binding post 24 while the other end of the switch conductor H is in contact with the outer end of the said conductor 22.

To supply current to the brush, signal and switch there is provided a wire conductor 25 extending from binding post 6 to said signal and battery of the vehicle.

Such modifications may be made as lie within the scope of the appending claims.

Having fully described my invention what I claim as new and desire to secure by Letters Patent is:

1. In an electric signal switch for a pneumatic tire carried by a rim of a wheel, the rim being bored through its center zone, a tubular housing of insulating material having a flanged head to close one end thereof, the head being bored axially with the housing, the other end of the housing being threaded internally, a metallic head to engage in the threaded end of the housing, said head being bored and threaded axially, the said head having an annular flange on its outer end to extend beyond the wall of the housing, a metallic sleeve through which the housing extends, said sleeve being moved toward the first said flange when the metallic head is screwed inward of the housing whereby when the housing is inserted through the bore of the rim the same is secured to the rim by its clamped engagement between first said flange and its adjacent end of the sleeve, a tubular plunger to slidably engage in-the bore of the first said head and a removable concave-convex head secured to one end of the plunger and a head integrally joined to the other end of the plunger and being within the housing in spaced relation from the inner side of said housing head, a metallic washer secured to the inner side of said housing head as a contact element for the inner head of the plunger, the peripheral bore of the washer being spaced from the plunger, a coil spring seating on the said inner head of the plunger, and an adjustable threaded stem to carry the other end of the coil spring whereby the spring is tensioned to engagement with the washer as closing means for electric circuit, the washer having an electric conductor connected thereto, said conductor extending to a signal and to a source of electric power, there being a pneumatic tube positioned in the tire to break the circuit when said tire is normall inflated.

2. In a means for securing an electric signal switch for pneumatic tires to a rim of a motor vehicle, said rim being bored through on its center zone, the securing means comprising a tubular housing made of insulating material, one end of which has a flanged head integrally joined there to, a metallic sleeve to engage slidably on the tube portion of the housing, a metallic flanged head externally threaded to close the other end of the tubular housing, said metallic head adapted to screw inward and outward at its respective end of the said housing whereby the flange of the metallic head will slide the sleeve toward the flange of the said tubular housing to clamp a bored rim of a wheel between the first said heads flange and its abutting end of the sleeve.

ERNIE W. CRANMER. 

